Pull tab for slide fastener and a slide fastener incorporating such pull tab

ABSTRACT

A pull tab for manipulating a slide of a slide fastener and a slide fastener incorporating such pull tab. The pull tab is made of a synthetic elastomer, wherein the synthetic elastomer is a polyether amide block copolymer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to a pull tab enabling the manipulationof the slider of a slide fastener, as well as a slide fastener equippedwith such a pull tab, and adapted especially for the closure of shoes,clothes, handbags and other items.

2. Discussion of Background and Relevant Information

Pull tabs for slide fasteners are traditionally constituted of ametallic material. In view of the substantial forces exerted often bythe user, they must in fact have great endurance to shock and torsion.But such metallic materials (various alloys, stainless steel, etc.) arerigid materials and, therefore, are almost incapable of deformation,torsion or flexion, which promote tearing of the connector bar, or adeformation of the critical portions of the pull tab, especially whenthe slide fasteners are located in areas that cannot be easily accessedby the user, such as winter sports boots, for example, wherein grippingwith gloves is not easy.

On the other hand, if the closure elements are torn off accidentally,the presence of metallic elements can result in injuries to the user.

Attempts to overcome these disadvantages were directed to consideringsynthetic materials that were presently commercially available and whichwere determined to be capable of overcoming the disadvantages of theprior state of the art regarding the manufacture of pull tabs for slidefasteners.

U.S. Patent No. 4,949,434 proposed the manufacture of pull tabs enablingmanipulation of the slider of a slide fastener, constituted of asynthetic material having properties of elasticity, such as a syntheticelastomer, and especially a polyester elastomer.

The amorphous phase of such copolymers is of the ester or ether type,whereas the rigid phase is of the polybutylene terphthalate type.

This choice of material does have disadvantages, however. In particular,polyester or polyether block ester elastomers are extremely sensitive toultra-violet radiation. Although their yellowing is limited, theirmechanical characteristics decrease sharply with prolonged exposure. Assuch, they must be provided with anti-UV protection by means ofappropriate additives.

On the other hand, they are often difficult to dye and their resistanceto wear and tear due to abrasion is not always satisfactory.

Also considered was the use of urethane polyether block copolymers. Inthese copolymers, the amorphous sequence is constituted by the reactionproduct of a long chain polyol having an isocyanate, while the rigidsequence results from the action of an isocyanate having a very shortglycol chain. This type of copolymer owes its reinforcing characteristicto the hydrogen links located between the polymer chains.

These copolymers have excellent resistance to traction as well as towear and tear by abrasion, but it must be noted that they becomesubstantially yellow under exposure to ultraviolet rays and also that alarge number of such polymer types display a pronounced rigidity at lowtemperatures.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a slide fastener,including a pull tab, which is not afflicted with the disadvantages ofthe prior art.

More particularly, it is an object of the invention to determine, amongsynthetic thermoplastic polymers, which are easier to work with thanthermohardenables, those that are suited for the manufacture of pulltabs for slide fasteners.

The selection criteria according to the invention were determined to bethe following:

ease of manufacture, by injection and/or molding;

ease of dyeing (this factor is very important for pull tabs, since pulltabs are adapted to be used on boots, bags and clothing where thefashion aspect is extremely important);

shiny appearance (once again for aesthetic reasons);

the material must display, in addition, the indispensablecharacteristics of elongation, flexibility, tenacity, endurance,resistance to shock and resistance to traction and torsion;

these characteristics must be retained at low temperatures (this factoris indispensable especially for articles adapted to be used in thesevere temperature conditions of winter sports); and

the materials retained should not be excessively sensitive toultra-violet rays.

With regard to the aforementioned objects of the invention, particularlywith regard to the determination of synthetic thermoplastic polymersthat are suited for the manufacture of pull tabs for slide fasteners andthe aforementioned selection criteria according to the invention, aninitial analysis tended to favor, among the numerous thermoplasticpolymers, those elastomers that are known to be easy to manufacture, ata substantial rate, and that are easy to transform with relativelysimple injection means, and that are, in addition, easy to dye.

Indeed, tests undertaken with some other rigid thermoplastic polymerssuch as polyoxymethylenes (POM) or polyacetals (of the type marketedunder the trademark DELRIN) did not provide satisfactory results; theseexcessively rigid materials ruptured during torsion tests. Moreover,they are sensitive to the effect of ultra-violet rays.

Thermoplastic elastomers are materials adapted to fulfill commonphysical characteristics, such as, for example, less rigidity,substantial elongation at tears, and in the majority of cases, a totalabsence of an elasticity threshold, corresponding to an extremelyamorphous product.

Their performance can be compared to those of traditional elastomers, ina wide temperature range, and they can also be shaped like thermoplasticpolymers.

Products corresponding to this definition include, in addition tosynthetic rubber, silicon elastomers as well as the entire range ofsequenced thermoplastic copolymers, such as polyether-urethane blockcopolymers, polyether-ester block copolymers and polyetheramide blockcopolymers.

These sequenced thermoplastic copolymers are, in fact, copolymers formedin two phases, one amorphous and the other crystalline, located insequences along the molecular chains.

By playing with electromagnetic interactions, the crystalline zones aregrouped in fields that are uniformly distributed in the amorphous zones.

At the working temperature, lower than the vitreous transitiontemperature T_(v) of the thermoplastic phase, the thermoplastic zonesconstitute the reversible physical cross-linking nodes which confer, tothese materials, a behavior similar to that of traditional elastomersafter vulcanization.

BRIEF DESCRIPTION OF THE DRAWING

In the single drawing FIGURE, a slide fastener including the pull tab,according to the invention, is shown in a perspective view in partialcross-section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In accordance with the invention, the slide fastener and the sliderattached thereto can be of any known type. As can be seen, for example,in the single drawing FIGURE, the slider 2 has a connector bar 3 towhich the pull tab 1 is secured, enabling the manipulation of slider 2.The base of the slider 2 cooperates in a traditional manner with slidefasteners 4.

A new selection of material according to the aforementioned selectioncriteria, made from among other block copolymers, proved that for theapplication according to the invention, polyether amide block copolymersare very appropriate, especially in view of their ease of dyeing andtheir improved resistance properties to wear and tear due to friction.

In these polyether amide block copolymers, the amorphous sequence isconstituted by an extremely amorphous ether phase which provides theflexibility properties.

The rigid sequence is obtained from Polyamide 6 or Polyamide 12 typechain sections.

The pull tab enabling the manipulation of the slider of a slide fasteneraccording to the invention, of the synthetic elastomer type, includes anelastomer chosen from among polyether amide block copolymers.

It is important to highlight the original properties of such copolymers,which proved to be particularly interesting in the field of applicationof the invention.

They have excellent qualities of flexibility, tenacity and endurance.Their shore hardness varies from 80 Sh A to 70 Sh D; their resistance toshock at low temperatures is very good.

On the other hand, their excellent flexibility in traction and inflexion, in temperatures ranging from -40° C. to +80° C. enables them tobe used under difficult circumstances whenever it is necessary toguarantee substantial deformations, which is indeed the case for pulltabs that are manipulated frequently in severe weather conditions.

Finally, these copolymers are especially easy to dye, and this enablesthe production of pull tabs in all fashionable shades, and their shinyappearance is very pleasant to behold.

The pull tab obtained from amide block copolymers in accordance with theinvention can be especially adapted to be utilized in connection withthe types of pull tabs described in commonly assigned French PatentPublication No. 2,656,511, published on Jul. 5, 1991. This pull tab can,regardless of the position of the slider along the slide fastener, beimmobilized with respect to the actual slider, in at least one stableposition, especially a neutral position, by application of the slidefastener.

By virtue of the material used in the present invention, one can varythe elasticity of the material, so that the transmission of the torsioncouple and flexional forces on the connector bar are reduced to almostnothing, and at the same time, the pull tab is provided with a greatersection and generally larger dimensions, especially in length, byincreasing its durability as well as ease of grip, even with a glovedhand.

The present invention is naturally not limited to only this type of pulltab for slide fasteners, and can find an application in other existingdesigns.

What is claimed is:
 1. A pull tab for manipulating a slider of a slidefastener, the pull tab comprising:a member made of a syntheticelastomer, said synthetic elastomer comprising a polyether amide blockcopolymer.
 2. A slide fastener comprising:a slider for opening andclosing said slide fastener; and a pull tab connected to said slider formanipulating said slider along the slide fastener, said pull tabcomprising a synthetic elastomer, said synthetic elastomer comprising apolyether amide block copolymer.